Method for optimizing reservoir production analysis

ABSTRACT

Optimizing reservoir production in a commingled hydraulically fractured reservoir by allocating commingled system production data to each of the individual completed intervals in the system, calculating the reservoir and fracture properties for each completed reservoir layer, and recalibrating the commingled and individual layer production data by accounting for the individual completed interval reservoir and fracture properties.

Embodiments relate to methods for optimizing the overall reservoir production. In particular, the the use of reservoir and fracture properties in the analysis of production performance of multilayer commingled reservoirs.

BACKGROUND ART

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. Reservoir characterization and well completion efficiency evaluation in a multilayer commingled system and well production performance data and periodic production log measurements is a very important task. Commingled well production data from a system with a number of different layers with varying reservoir and well completion properties should not in general be evaluated using an equivalent single layer reservoir analog. The results of such an analysis for determining estimates of the reservoir properties and completion efficiencies of each of the individual reservoir layers in this case will be very inaccurate.

There are various methods of allocating commingled production data for individual reservoir layer production performance analyses. One of the most efficient and reliable methods of allocating the commingled well production data to the individual completed intervals in the system is by using periodically obtained multi-rate production logging information. The allocation of the commingled production data to generate the individual completed interval production histories is required for the proper evaluation of the reservoir properties and well completion properties for every layer, such as the reservoir effective permeability, well effective drainage area, and steady state skin effect. In the case of a hydraulically fractured completed reservoir layer in the well, it permits the proper evaluation in each completed reservoir layer of such properties as the average effective fracture conductivity and the effective fracture half-length.

The data used in this analysis method are the commingled reservoir system production data (fluid phase flow rates), the wellhead flowing temperatures and pressures, the complete wellbore and tubular goods description and production log information. These values are used in a computational analysis to construct the equivalent individual completed interval production histories that can subsequently be used for the evaluation of the reservoir and completion properties in each of the completed reservoir layers. Obviously, many of these reservoir and well completion properties also affect the allocation of the commingled reservoir production data.

U.S. Pat. No. 6,101,447, U.S. Pat. No. 6,691,037, U.S. Pat. No. 6,842,700, U.S. Pat. No. 5,960,369 and U.S. Pat. No. 6,571,619, each incorporated herein by reference, propose methods for obtaining improved well production optimization based on type curves methods, history matching, and other methods for reducing the non-uniqueness of solution. These methods can be applied to different types of reservoirs, such as a conventional reservoir, a tight gas reservoir, and where only incomplete pressure/rate history records are available. These methods only consider that the production performance of a single reservoir layer in the system.

It is an object herein to provide an improved methodology that can be applied to multi-layer reservoir systems.

SUMMARY

Accordingly, a first aspect includes a method for optimizing reservoir production in a commingled hydraulically fractured reservoir by:

allocating commingled system production data to each of the individual completed intervals in the system;

calculating the reservoir and fracture properties for each completed reservoir layer;

recalibrating the commingled and individual layer production data by accounting for the individual completed interval reservoir and fracture properties.

In some cases, the reservoir and fracture properties are calculated using the transient and stabilized inflow performance relationship established using the multi-rate production log information.

The individual layer production data may be accounted for by using approximate values of the reservoir and/or fracture properties and then updating and correcting the relative input parameter estimates for every layer in the commingles reservoir system.

The reservoir and fracture properties may include effective permeability, initial reservoir pressure, reservoir effective drainage area, steady state skin effect, average fracture conductivity and/or effective fracture half-length.

The production data may include commingled well production data, wellhead flowing temperatures and/or pressures, the description of the complete wellbore and its tubular components and/or production log information.

In some cases, allocating commingled production data to of the completed intervals in the system includes using multi-rate production log information.

Methods may further include using the well production performance data derived for each layer in the commingled system for further production performance optimization and forecasting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart of the workflow for the optimisation of overall reservoir production.

DESCRIPTION OF SOME ILLUSTRATIVE EMBODIMENTS

At the outset, it should be noted that in the development of any such actual embodiment, numerous implementation—specific decisions must be made to achieve the developer's specific goals, such as compliance with system related and business related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

Some embodiments described herein provide methods to maximize the efficiency of the reservoir production data analysis by using the allocation of the commingled production data in a commingled multilayer hydraulically fractured reservoir with multi-rate production log information.

An additional step in the production data allocation using modern multi-rate production logs to establish the inflow performance behaviour of each of the completed intervals in the well is performed to maximise the efficiency of the reservoir production data analysis. The additional step involves the calculation of the reservoir and fracture properties for each completed reservoir layer from the inflow performance behaviour of each of the completed intervals in the system and the further recalibration of the production data allocation taking into account the reservoir and fracture properties. This results in a more reliable production performance allocation for each completed layer in the system, and as a result a better optimization of the overall reservoir production.

The commingled system performance data allocation process takes into account the reservoir and fracture properties such as the effective permeability, initial reservoir pressure, reservoir effective drainage area, steady state skin effect, average fracture conductivity, and effective fracture half-length.

By being able to use these properties in the production data allocation process leads to more reliable computation of the production performance data of each of the layers in the commingles multilayer reservoir. More reliable calculation of the production performance data for each layer in the commingled system leads to improved efficiency and accuracy of the production forecasts of the commingles system, as well as optimum efficiency obtained in the well stimulation candidate recognition process.

FIG. 1 shows a flow chart of the workflow for the in accordance with an embodiment of the invention. In the first step 10 the commingled production data in multilayer reservoir is properly allocated to each of completed intervals in the system using multi-rate production log information. U.S. Pat. No. 7,062,420 and U.S. Pat. No. 7,089,167, incorporated herein by reference, describe methods of allocating data to multilayer commingled reservoirs. The production allocation methodology requires the commingled well production data, the well head flowing temperature and pressures, the wellbore completion and tubular component descriptions, and production log information.

The next step 12 is the validation of the production log information. If only production log information for a single well flow rate is only available then the workflow in this invention is not applicable 14 and the computations are terminated. Otherwise if multi-rate production log information is available then the analysis can proceed to the next step 16.

If the required reservoir and fracture properties are already known or can be readily obtained via another means then you can then proceed to the next step 20. If not the reservoir and fracture properties for each layer are calculated 18. The reservoir and fracture properties are calculated using the transient and stabilized inflow performance relationship based in the multi-rate production log information. Such methods are described in SPE 104018 and SPE 68141.

Once reservoir and production properties are available the next step 20 is recalibrating the of the commingled and individual layer production performance histories by accounting for the individual completed interval reservoir and fracture properties that are already known or previously calculated. This may be done by approximating the values of some of the reservoir and/or fracture properties and then subsequently updating and correcting the relative input parameter estimates for every layer in the commingled reservoir system.

This results in well production performance values for each layer in the commingled reservoir system. These values can be used 22 separately for further or additional production performance optimization and forecasting purposes.

The methodology allows consideration of non-Darcy fluid flow in the reservoir or hydraulic fractures in the individual layer performance analysis can also be taken into account to more accurately and reliably establish the reservoir and well completion properties for highly productive oil and gas producing formation in the commingled multilayered reservoir system.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. 

1. A method comprising: allocating commingled system production data to each of the individual completed intervals in the system; calculating the reservoir and fracture properties for each completed reservoir layer; and, recalibrating the commingled and individual layer production data by accounting for the individual completed interval reservoir and fracture properties.
 2. A method according to claim 1 wherein the reservoir and fracture properties are calculated using the transient and stabilized inflow performance relationship established using the multi-rate production log information.
 3. A method according to claim 1 wherein accounting for the individual layer production data comprises using approximate values of the reservoir and/or fracture properties and then updating and correcting the relative input parameter estimates for every layer in the commingles reservoir system.
 4. A method according to claim 1 wherein the reservoir and fracture properties comprise effective permeability, initial reservoir pressure, reservoir effective drainage area, steady state skin effect, average fracture conductivity and/or effective fracture half-length.
 5. A method according to claim 1 wherein the production data comprises commingled well production data, wellhead flowing temperatures and/or pressures, the description of the complete wellbore and its tubular components and/or production log information.
 6. A method according to claim 1 wherein allocating commingled production data to of the completed intervals in the system comprises using multi-rate production log information.
 7. A method according to claim 1 further comprising using the well production performance data derived for each layer in the commingled system for further production performance optimization and forecasting.
 8. A method according to claim 1 wherein accounting for the individual layer production data comprises using approximate values of the reservoir and/or fracture properties and then updating and correcting the relative input parameter estimates for every layer in the commingles reservoir system.
 9. A method according to claim 1 whereby reservoir production in a commingled hydraulically fractured reservoir optimized.
 10. A method comprising: allocating commingled system production data to each of the individual completed intervals in the system; and, calculating the reservoir and fracture properties for each completed reservoir layer; whereby reservoir production in a commingled hydraulically fractured reservoir optimized.
 11. A method according to claim 10 further comprising recalibrating the commingled and individual layer production data by accounting for the individual completed interval reservoir and fracture properties.
 12. A method according to claim 11 wherein the recalibrating is conducted by approximating the values of some of the reservoir and/or fracture properties and then subsequently updating and correcting the relative input parameter estimates for every layer in the commingled reservoir system.
 13. A method according to claim 10 wherein the reservoir and fracture properties are calculated using the transient and stabilized inflow performance relationship established using the multi-rate production log information.
 14. A method according to claim 10 further comprising considerating non-Darcy fluid flow in the reservoir or hydraulic fractures in an individual layer performance analysis.
 15. A method according to claim 10 wherein the reservoir and fracture properties comprise effective permeability, initial reservoir pressure, reservoir effective drainage area, steady state skin effect, average fracture conductivity and/or effective fracture half-length.
 16. A method comprising: allocating commingled system production data to each of the individual completed intervals in the system; calculating the reservoir and fracture properties for each completed reservoir layer; and, recalibrating the commingled and individual layer production data, wherein the production data includes any one or more of commingled well production data, wellhead flowing temperatures and/or pressures, the description of the complete wellbore and its tubular components, and production log information.
 17. A method according to claim 16 whereby reservoir production in a commingled hydraulically fractured reservoir optimized.
 18. A method according to claim 16 wherein the reservoir and fracture properties are calculated using the transient and stabilized inflow performance relationship established using the multi-rate production log information.
 19. A method according to claim 16 further comprising considering non-Darcy fluid flow in the reservoir or hydraulic fractures in an individual layer performance analysis.
 20. A method according to claim 16 wherein the reservoir and fracture properties comprise effective permeability, initial reservoir pressure, reservoir effective drainage area, steady state skin effect, average fracture conductivity and/or effective fracture half-length. 